The present invention is in the field of instrumentation, and more particularly, relates to weight measuring apparatus.
A typical prior art weighing system includes a platform, or weighing pan, for receiving the weight to be measured. The weighing pan is coupled by a force transducer to a support member, or frame. In various forms of the prior art, the transducer and weighing pan are coupled to the support member by linkages adapted to permit relatively accurate weighing of objects placed in the pan. By way of example, the force sensors might incorporate strain gauges, or a movable coil in a fixed magnetic field in a feedback arrangement.
While prior art weighing systems do provide a relatively accurate measure the weight of objects placed in the weighing pan, they have a number of shortcomings. For example, many such systems are particularly sensitive to off-center loading of the object-to-be-measured in the weighing pan. Such off-center loading may give rise to errors due to frictional losses in the system. To counteract such losses, the prior art scale systems often utilize various forms of mechanical linkages for reducing such errors. For example, U.S. Pat. No. 4,026,416 discloses a flexure arrangement restricting motion of the weighing pan along a single sensing axis. However, such systems are relatively limited in their range of motion and thus in the range of weights permitted.
A further disadvantage of many of the prior art systems, is variation of the indicated weight of a given object with temperature, such as may be due to the temperature effects on the sensing transducer and associated circuitry.
Accordingly, it is an object of the present invention to provide a high accuracy and high precision weighing system.
It is another object to provide a weighing system which is compensated for variations in temperature of the system.